An isopropylmethylphenol is widely used for products such as medicaments, quasi-drugs and cosmetics, as their agents such as an antibacterial agent, a bactericidal agent, and an antiseptic. Isomers exist in an isopropylmethylphenol; among them, a 4-isopropyl-3-methylphenol (hereinafter described as p-thymol in some cases) has characteristics such that its antibacterial and bactericidal activities are strong, as well as its toxicity against skin irritation is low, and it is colorless and odorless.
A method in which an m-cresol is reacted with propylene under presence of a catalyst so as to be isopropylated is known as a producing method for an isopropylmethylphenol. In this method, a 4-isopropyl-3-methylphenol, a 6-isopropyl-3-methylphenol (hereinafter described as o-thymol in some cases), a 5-isopropyl-3-methylphenol (hereinafter described as m-thymol in some cases), and a 2-isopropyl-3-methylphenol (hereinafter described as vic-thymol in some cases) that are isomers are produced. Accordingly, a 4-isopropyl-3-methylphenol has been presently produced by reacting an m-cresol with propylene under presence of a catalyst so as to obtain a mixture of the isomers, and then these mixture undergoing refinement controls such as isomerization, distillation, extracting, and crystallization, in general.
As for a producing method for an isopropylmethylphenol from an m-cresol and propylene, for example, a method using calcium oxide as a catalyst (Patent Document 1), a method using a metal sulfate and γ-alumina as a catalyst (Patent Document 2), and a method using a catalyst solution including a zinc bromide, hydrogen bromide and water (Patent Document 3) are known.
Also, a method in which a phosphoric acid is brought to coexist in a reaction of an m-cresol with propylene is known. For example, reported method is such that a phosphoric compound selected from a group consisting of a phosphoric anhydride, condensed phosphoric acid and salt thereof, and a phosphoric acid and salt thereof is brought to coexist in producing alkyl phenols by reacting phenols such as an m-cresol with olefins such as a propylene, using an activated clay or acid clay as a catalyst in liquid phase (Patent Document 4). Further, a method also reported is such that an m-cresol is reacted with propylene under presence of a catalyst that is a solid phosphate catalyst in which at least one kind of a carrier selected from a group consisting of silica-alumina, diatomaceous earth, and silica-titania are supported by a phosphoric acid at the specific ratio; the reaction is conducted in a heated liquid phase and under condition of the specific propylene pressure, so as to produce thymols that has a p-thymol and o-thymol mainly and the production ratio of o-thymol/p-thymol is 3/1 or less (Patent Document 5).
Also, reported method is such that an m-toluidine is isopropylated under presence of a sulfuric acid so as to be a methyl-4-isopropylaniline, then the methyl-4-isopropylaniline is diazo-decomposed or hydrolyzed under high temperature and high pressure to produce a 4-isopropyl-3-methylphenol (Patent Document 6).